Spy is an ability exclusive to Jeff in EarthBound. When used in battle, it will display the foe's attack and defense stats, alongside one of their PSI weaknesses. It can also be used to steal items from enemies (if they possess item). It is very useful when hunting for "1/128" items, thus defeating the enemy is unnecessary. Note that if you don't get an item by spying the first time, the enemy most likely does not have one at all.